1. Field of the Invention
The present invention is directed to the use of at least one C-nitrosoaniline compound and/or quinone imine oxime, alone or in combination with at least one stable nitroxide free radical compound, and/or at least one nitroaromatic compound, and/or at least one quinone alkide compound, preferably a quinone methide, and/or at least one quinone compound, and/or at least one hydroquinone compound, and/or at least one hydroxylamine compound, and/or at least one phenylenediamine compound, and/or air or oxygen to inhibit the polymerization of ethylenically unsaturated monomers.
2. Description of Related Art
Many ethylenically unsaturated monomers undesirably polymerize at various stages of their manufacture, processing, handling, storage, and use. A particularly troublesome problem is equipment fouling caused by polymerization in the purification stages of the production processes of such monomers. Polymerization, such as thermal polymerization, during their purification results in the loss of the monomer and a loss in production efficiency owing to the deposition of polymer in or on the equipment being used in the purification, the deposits of which must be removed from time to time. Additionally, the formation of soluble polymer leads to loss of monomer, i.e., a lower yield, and an increase in the viscosity of any tars that may be produced. The processing of the tars then requires higher temperature and work (energy cost) to remove residual monomer.
A wide variety of compounds has been proposed and used for inhibiting uncontrolled and undesired polymerization of ethylenically unsaturated monomers. There remains a need, however, for an inhibitor that not only provides highly effective inhibition of polymerization during normal operation of a continuous manufacturing or purification process, but also provides satisfactory protection in the event of a loss of continuous inhibitor feed. While many inhibitors are known to provide sufficient protection in one of these scenarios, they have not been fully satisfactory under both normal and upset operating conditions. Accordingly, a substantial need continues in the art for improved compositions for inhibiting the polymerization of such monomers during their production and during the distillation process for purifying or separating them from impurities, as well as during transport and storage.
Aromatic nitroso and di-nitroso compounds are known to be useful as chemical agents capable of promoting the formation of filler-elastomer linkages. The aromatic nitroso compounds may be aromatic amines, including polyamines or phenolic compounds. They are also known to be useful intermediates in the production of other chemicals, such as p-aminodiphenylamine.
U.S. Pat. Nos. 3,988,212 and 4,341,600 disclose the use of N-nitrosodiphenylamine combined with dinitro-cresol derivatives for inhibiting the polymerization of vinyl aromatic compounds under vacuum distillation conditions.
U.S. Pat. No. 4,362,893 discloses that C-nitrosodiarylamines may be prepared in a single stage from diarylamines by adding alcoholic solutions of a hydrogen halide below the surface of a stirred mixture of the diphenylamine in an organic liquid containing water.
U.S. Pat. No. 4,479,008 discloses a process for preparing p-nitrosodiphenylamine hydrochloride from N-nitrosodiphenylamine and hydrogen chloride. The product is prepared in the absence of an aromatic solvent and using a solvent consisting essentially of aliphatic C5-C10 alcohol.
U.S. Pat. No. 4,518,803 discloses a process for the preparation of p-nitrosodiphenylamine hydrochloride comprising reacting diphenylamine, C5-C10 alkyl nitrite and anhydrous HCl in the presence of a C5-C10 aliphatic alcohol and essentially in the absence of an aromatic solvent.
U.S. Pat. No. 5,001,171 discloses that uncured modified rubber compositions comprising mixtures of elastomers and a reinforcing filler can be prepared by a process which comprises, inter alia, the use of at least one chemical agent capable of promoting the formation of filler-elastomer linkages. Examples of such useful chemical agents include aromatic furazan oxides, heterocyclic di-N-oxides, 1-hydroxy-benzimidazole-3-oxide compounds, 1,3-dihydroxy-benzimidazolinone compounds, and aromatic nitroso compounds.
U.S. Pat. No. 5,623,088 discloses a method of producing 4-aminodiphenylamine (4-ADPA) wherein aniline or substituted aniline derivatives and nitrobenzene are reacted under suitable conditions to produce 4-nitrodiphenylamine or substituted derivatives thereof and/or their salts, either or both of which are subsequently reduced to produce 4-ADPA or substituted derivatives thereof. The 4-ADPA or substituted derivatives thereof can be reductively alkylated to produce p-phenylenediamine products or substituted derivatives thereof which are useful as antiozonants. A second embodiment of the invention is the tetrasubstituted ammonium salts or alkyl substituted diammonium salts of 4-nitrodiphenylamine, 4-nitrosodiphenylamine and the substituted derivatives thereof wherein each substituent of the tetrasubstituted ammonium ion is independently selected from the group consisting of alkyl, aryl and arylalkyl groups and each alkyl substituent of the alkyl substituted diammonium salt is independently selected.
U.S. Pat. No. 5,648,543 discloses a process for producing a 4-nitrosodiphenylamine of the formula wherein R1 and R2 independently represent hydrogen atom, methyl group, ethyl group, cyclohexyl group, methoxy group, ethoxy group or chlorine or bromine atom, or a salt thereof, comprising treating a diphenylamine represented by the formula wherein R1 and R2 are as defined above with (i) a mixture of nitrogen oxides, (ii) a hydrogen halide and (iii) an aliphatic alcohol, wherein the atomic ratio of oxygen to nitrogen of the mixture of nitrogen oxides is more than 1.0 and less than 2.0.
U.S. Pat. No. 5,739,403 discloses the production of 4-aminodiphenylamines by reacting optionally substituted aniline with optionally substituted nitrobenzene in the presence of water and/or alcohols and organic and/or inorganic bases and then catalytically hydrogenating the resultant nitro- and/or nitrosodiphenylamine in the presence of water. The catalytic hydrogenation of the reaction mixture is performed in the presence of 25 to 80 weight percent of water, relative to the weight of the reaction mixture from the condensation reaction, the hydrogenation catalyst is removed from the hydrogenation mixture once absorption of hydrogen has ceased, 10 to 100 vol. percent of aromatic solvent, relative to the total volume of the hydrogenation mixture, is optionally added to the hydrogenation mixture, the resultant organic phase is separated in order to isolate the 4-aminodiphenylamine and the aqueous phase is returned to the initial reaction mixture.
Quinone methides, quinones, hydroquinones, hydroxylamines, and nitroxyl compounds are known polymerization inhibitors.
Quinone methides act mainly as retarders, giving a significant amount of polymer during normal inhibition usage but providing protection in the event of a plant upset during monomer purification by slowing the rate of polymer formation under static conditions. Because of the poor normal inhibition performance, quinone methides must be used in fairly high dosages, making them not very economical to use.
U.S. Pat. Nos. 4,003,800 and 4,040,911 disclose the use of quinone alkides in a styrene purification process.
The following patents, assigned to Ciba-Geigy Corporation or Ciba Specialty Chemicals Corporation, relate to quinone methides and uses thereof.
U.S. Pat. Nos. 5,583,247, 5,670,692, and 5,750,765 disclose the protection of ethylenically unsaturated monomers from premature polymerization during manufacture and storage by the incorporation therein of an effective stabilizing amount of a quinone methide compound having an electron withdrawing substituent at the 7-methylene group.
U.S. Pat. No. 5,616,774 discloses the protection of ethylenically unsaturated monomers from premature polymerization during manufacture and storage by the incorporation therein of an effective stabilizing amount of a 7-aryl quinone methide compound wherein the 7-aryl substituent is 2-, 3-, or 4-pyridyl, 2- or 3-thienyl, 2- or 3-pyrryl, 2- or 3-furyl, aryl of six to 10 carbon atoms, or said aryl substituted by one to three alkyl of one to eight carbon atoms, alkoxy of one to eight carbon atoms, alkylthio of one to eight carbon atoms, alkylamino of one to eight carbon atoms, dialkylamino of two to eight carbon atoms, alkoxycarbonyl of two to eight carbon atoms, hydroxy, nitro, amino, cyano, carboxy, aminocarbonyl, chloro, or mixtures of said substituents. The combination of these quinone methides with at least one stable nitroxyl compound is also disclosed.
U.S. Pat. No. 5,912,106 discloses a method of improving the quality and resolution of photoimages by incorporating into the photocurable resin composition to be used a selected amount of a polymerization inhibitor so that photopolymerization of the photocurable resin is inhibited in those areas not directly impinged by light. Inhibitors that can be used are selected from the group consisting of N-oxyl or nitroxide compounds, quinone methides, nitroso compounds, phenothiazine and selected phenols.
Hindered nitroxyl compounds are known to be very active inhibitors of free radical polymerizations of unsaturated monomers such as styrene, acrylic acid, methacrylic acid, and the like.
U.S. Pat. No. 3,163,677 discloses N,N,O-trisubstituted hydroxylamines and N,N-disubstituted nitroxides of the formulas: wherein R1, R2, and R3 are each an alkyl radical having 1 to 15 carbon atoms. (As used herein, the designation N—O* denotes a stable free radical wherein the asterisk is an unpaired electron.) The N,N,O-trisubstituted hydroxylamines can be used to make the N,N-disubstituted nitroxides, which are stable free radicals and are said to be useful as polymerization inhibitors.
U.S. Pat. No. 3,267,132 discloses that the polymerization of unsaturated nitrites can be greatly inhibited by incorporating therein a minor amount of a nitroso compound selected from the group consisting of p-nitrosodiarylamines and N-nitrosoarylamines.
U.S. Pat. No. 3,334,103 discloses that nitroxides can be prepared from the corresponding heterocyclic amine wherein the nitrogen atom of the nitroxide group is attached to other than a tertiary carbon of an aliphatic group (i.e., the nitrogen atom forms a part of a heterocyclic nucleus). These nitroxides are said to have useful properties similar to those described for the N,N-disubstituted nitroxides of U.S. Pat. No. 3,163,677.
U.S. Pat. No. 3,372,182 discloses that a great variety of N,N-disubstituted, stable, free radical nitroxides not otherwise readily available can be prepared by a simple and convenient process that comprises pyrolyzing in an inert reaction medium virtually any hydroxylamine that is susceptible to cleavage of the O—C bond, e.g., tri-t-butylhydroxylamine.
U.S. Pat. No. 3,422,144 discloses stable, free radical nitroxides of the formula: wherein R is selected from the group consisting of tertiary alkyl, aryl, alkaryl, haloaryl, carboxyaryl, alkoxyaryl, alkylthioaryl, pyridyl, and dialkylaminoaryl, and R′ is tertiary alkyl. These nitroxides are said to be useful as traps for reactive free radicals both in the counting of free radicals and for inhibiting oxidation and free radical polymerization.
U.S. Pat. No. 3,494,930 discloses free radicals of the nitroxide type for use as initiators of free radical reactions, collectors of free radicals, polymerization inhibitors or antioxidants. They are constituted by nitrogenous bicyclic compounds in which one of the bridges comprises solely the nitroxide radical group and, in particular, by aza-9-bicyclo (3,3,1) nonanone-3-oxyl-9, and by aza-9-bicyclo (3,3,1) nonane oxyl-9.
U.S. Pat. No. 3,966,711 teaches that 2,2,7,7-tetraalkyl- and 2,7-dispiroalkylene-5-oxo-1,4-diazacycloheptanes substituted in the 4-position by mono- or tetravalent radicals are powerful light-stabilizers for organic polymers. They are said to possess higher compatibility than their 4-unsubstituted homologues, from which they can be synthesized by reactions known for N-alkylation. Preferred substituents in the 4-position are alkyl, alkylene, alkenyl, aralkyl, and esteralkyl groups. The 1-nitroxyls derived from the imidazolidines by oxidation with hydrogen peroxide or percarboxylic acids are also said to be good light stabilizers.
U.S. Pat. No. 4,182,658 discloses a method for preventing the polymerization of a readily polymerizable vinyl aromatic compound during distillation at elevated temperatures within a distillation apparatus that is subject to an emergency condition, such as a power outage. This method comprises force-feeding a supplemental polymerization inhibitor having a high solubility in the vinyl aromatic compound and a long duration of efficiency into each of the distillation vessels of a conventional distillation apparatus in an amount sufficient to prevent polymerization therein.
U.S. Pat. No. 4,665,185 discloses a process for the efficient preparation of nitroxyls of sterically hindered amines by the oxidation of the amine using a hydroperoxide in the presence of a small amount of a metal ion catalyst, at moderate temperature for a short period of time, to give the nitroxyl in high yield and purity.
U.S. Pat. No. 4,774,374 discloses a vinyl aromatic composition stabilized against polymerization comprising (a) a vinyl aromatic compound and (b) an effective amount of a stabilizer system in which the active ingredient consists essentially of an oxygenated species formed by the reaction of oxygen and an N-aryl-N′-alkyl-p-phenylenediamine. Also disclosed is a process for inhibiting the polymerization of vinyl aromatic compounds employing such an oxygenated species.
U.S. Pat. No. 5,254,760 teaches that the polymerization of a vinyl aromatic compound, such as styrene, is very effectively inhibited during distillation or purification by the presence of at least one stable nitroxyl compound together with at least one aromatic nitro compound.
U.S. Pat. No. 5,504,243 discloses a method for inhibiting polymerizable (meth)acrylic acid and esters thereof from polymerizing during their production, transportation and storage by using as the inhibitor N-oxyl compound and more than one compound selected from the group consisting of manganese salt compound, copper salt compound, 2,2,6,6,-tetramethylpiperidine compound and nitroso compound. The N-oxyl compound is one or more kinds selected from 2,2,6,6,-tetramethylpiperidinooxyl, 4-hydroxy-2,2,6,6,-tetramethylpiperidinooxyl and 4,4′,4″-tris-(2,2,6,6,-tetramethylpiperidinooxyl)phosphite. The combined use of the inhibitors is said to provide a superior inhibiting effect to use alone.
U.S. Pat. Nos. 5,545,782 and 5,545,786 disclose that nitroxyl inhibitors in combination with some oxygen reduce the premature polymerization of vinyl aromatic monomers during the manufacturing processes for such monomers. Even small quantities of air used in combination with the nitroxyl inhibitors are said to result in vastly prolonged inhibition times for the monomers.
U.S. Pat. No. 5,711,767 discloses that the use of nitroxide compounds alone or in combination with aromatic amines, such as substituted phenylenediamines, or phenolic antioxidants provides an effective way to prevent oxidative degradation and gum formation in gasolines.
U.S. Pat. No. 5,910,232 teaches that inhibition performance in styrene processing is improved through the addition of a stable nitroxide free radical compound to the styrene feed and to the reflux of at least one column. A nontoxic retarder, such as phenylenediamine, may also optionally be added to the styrene feed and to the reflux.
U.K. Patent Number 1,127,127 discloses that acrylic acid can be stabilized against polymerization by the addition thereto of a nitroxide having the essential skeletal structure: wherein R1, R2, R3, and R4 are alkyl groups and no hydrogen is bound to the remaining valencies on the carbon atoms bound to the nitrogen. The two remaining valencies that are not satisfied by R1 to R4 or nitrogen can also form part of a ring (e.g., 2,2,6,6 tetramethyl-4-hydroxy-piperidine-1-oxyl).
European Patent Application 0 178 168 A2 discloses a method for inhibiting the polymerization of an α,β-ethylenically unsaturated monocarboxylic acid during its recovery by distillation by using a nitroxide free radical.
European Patent Application 0 765 856 A1 discloses a stabilized acrylic acid composition in which the polymerization of the acrylic acid is inhibited during the distillation process for purifying or separating the acrylic acid as well as during transport and storage. The compositions comprise three components: (a) acrylic acid, (b) a stable nitroxyl radical, and (c) a dihetero-substituted benzene compound having at least one transferable hydrogen (e.g., a quinone derivative such as the monomethyl ether of hydroquinone (MEHQ)). During the distillation process, transport, and storage, components (b) and (c) are present in a polymerization-inhibiting amount. During the distillation process, oxygen (d) is preferably added with components (b) and (c).
WO 97/46504 concerns substance mixtures containing: (A) monomers containing vinyl groups; and (B) an active amount of a mixture which inhibits premature polymerization of the monomers containing vinyl groups during their purification or distillation and contains: (i) between 0.05 and 4.5 weight percent, relative to the total mixture (B), of at least one N-oxyl compound of a secondary amine which has no hydrogen atom at the α-C atoms; and (ii) between 99.95 and 95.5 weight percent relative to the total mixture (B), of at least one nitro compound. The publication also discloses a process for inhibiting the premature polymerization of monomers, and the use of mixture (B) for inhibiting the premature polymerization of monomers.
WO 98/14416 discloses that the polymerization of vinyl aromatic monomers such as styrene is inhibited by the addition of a composition of a stable hindered nitroxyl radical and an oxime compound.
WO 98/25872 concerns substance mixtures containing: (A) compounds containing vinyl groups; (B) an active amount of a mixture which inhibits premature polymerization of the compounds containing vinyl groups and contains: (i) at least one N-oxyl compound of a secondary amine which does not carry any hydrogen atoms on the α-carbon atoms; and (ii) at least one iron compound; (C) optionally nitro compounds; and (D) optionally co-stabilizers. The publication also discloses a process for inhibiting the premature polymerization of compounds (A) containing vinyl groups, and the use of (B) optionally mixed with nitro compounds (C) and/or co-stabilizers (D) for inhibiting the premature polymerization of radically polymerizable compounds and stabilizing organic materials against the harmful effect of radicals.
WO 99/20584 discloses that polymerization can be inhibited during the anaerobic production of styrene through the addition of a combination of a stable nitroxide free radical compound and a nontoxic phenylenediamine compound.
CS-260755 B1 is directed to the preparation of 4-substituted-2,2,6,6-tetramethylpiperidine nitroxyls as olefin stabilizers.
Hung. 150,550 discloses that free radical polymerization was inhibited with organic nitroso compounds, e.g., p-H2NC6H4NO (I), α-nitroso-β-naphthol, or β-nitroso-α-naphthol. For example, addition of 0.3 grams of (I) to one liter of styrene is said to have resulted in the stability of the latter for months. Also, (I) could be removed with azodiisobutyronitrile.
SU-334845 A1 is directed to the inhibition of the radical polymerization of oligoester acrylates using iminoxyl radical inhibitors of a given formula.
SU-478838 is directed to the inhibition of the radical polymerization of oligoester acrylates and the prevention of oligomeric peroxides using a binary polymerization inhibitor comprising quinone.
FR 2,761,060 relates to the prevention of premature polymerization of styrene during its production by dehydrogenation of ethylbenzene by injecting into the process effluent a radical inhibitor based on an oxyl-tetramethylpiperidine derivative.
U.S. Pat. No. 4,086,147 discloses a process using 2-nitro-p-cresol as a polymerization inhibitor.
U.S. Pat. Nos. 4,105,506 and 4,252,615 disclose a process using 2,6-dinitro-p-cresol as a polymerization inhibitor.
U.S. Pat. Nos. 4,132,602 and 4,132,603 disclose the use of a halogenated aromatic nitro compound as a polymerization inhibitor for use during the distillation of vinyl aromatic compounds.
U.S. Pat. No. 4,466,904 discloses the use of phenothiazine, 4-tert-butylcatechol and 2,6-dinitro-p-cresol as a polymerization inhibitor system in the presence of oxygen during heating of vinyl aromatic compounds.
U.S. Pat. No. 4,468,343 discloses a composition and a process for utilizing 2,6-dinitro-p-cresol and either a phenylenediamine or 4-tert-butylcatechol in the presence of oxygen to prevent the polymerization of vinyl aromatic compounds during heating.
European patent application 240,297 A1 teaches the use of a substituted hydroxylamine and a dinitrophenol to inhibit the polymerization of a vinyl aromatic compound at elevated temperatures in a distillation process.
Georgieff, K. K., J. Appl. Polymer Sci. 9(6):2009-18 (1965) measured the inhibitory effect of the following compounds on the bulk polymerization of methyl methacrylate: hydroquinone, p-tert-butylcatechol, p-methoxyphenol, 2,4-dichloro-6-nitrophenol, n-propyl gallate, di-tert-butyl-p-cresol, 2,2′-methylenebis(4-methyl-6-tert-butylpbenol), 1-amino-7-naphthol, p-benzoquinone, 2,6-dichloro-p-benzoquinone, 2-amino-1,4-naphthoquinone, three aminoanthraquinones, diphenylamine, p-nitrosodimethylaniline, α- and β-naphthylamine, phenothiazine, N-nitroso-dimethylamine, hexamethylphosphoramide, n-dodecyl mercaptan, benzenethiol, 2,2-diphenyl-1-picrylhydrazyl, phenyl hydrazine, divinylacetylene, and various antimony and copper salts. Polymerization was carried out in a test tube in a bath at 101.2° C., benzoyl peroxide being used as initiator. Generally, phenols and naphthols were the strongest inhibitors, followed by quinones, aromatic amines, 2,2-diphenyl-1-picrylhydrazyl, antimony pentachloride, phenyl hydrazine, divinylacetylene, and the thiols.
Additionally, see also:
    JP 62187710 (1987) which includes a C-nitrosoaniline derivative as a polymerization inhibitor of acrylamides at 100° C.;    JP 58014424 (1983) which includes a C-nitrosoaniline derivative as a polymerization inhibitor of aqueous solutions of acrylate esters;    JP 45017652 (1970) which includes a C-nitrosoaniline derivative as a polymerization inhibitor of aqueous solution of acrolein or methacrolein;    JP 49125315 (1974) which includes C-nitrosodiphenylamine as a polymerization inhibitor of methacrylate and acrylate esters;    JP 53-33578 (1978) which includes C-nitrosodiphenylamine as a polymerization inhibitor; and    Boguslavskaya, L. S., Khim. Prom-st. 43(10):749-52 (1967).
Several articles have described the use of C-nitrosoaniline derivatives as inhibitors of AIBN- or benzoylperoxy-initiated polymerizations of styrene, methylacrylate, methyl methacrylate, acetonitrile, and their copolymers, e.g.,    Tudos, F. et. al., Eur. Polym. J., 18(4):295-9(1982);    Ibid., 19(7):593-5 (1983);    Ibid., 8(11):1281-9 (1972);    Ibid., 30(12):1457-9 (1994);    Ibid., 19(3):225-9 (1983);    Ibid., 19(2):153-7 (1983);    Ibid., 18(6):487-91 (1982);    Tudos, F., Proc. IUPAC Macromol. Symp., 28th, 90 (1982);    Tudos, F. et. al., Kinet. Mech. Polyreactions, Int. Symp. Macromol. Chem., Prepr., 5(25):109-113 (1969);    Yoneda, A. et al., Kobunshi Kagaku, 27(300):269-75 (1970); and    Zaitsev, Y. S. et al., Dopov, Akad. Nauk Ukr. RSR, Ser. B: Geol., Khim. Biol. Nauki, (11):988-91 (1977).
The foregoing are incorporated herein by reference in their entirety.